Why Tolerance Isn't Possible

Someone explain to me why tolerance is a GOOD thing for people who deny reality. Someone explain to me how it is that, "Everyone is entitled to their beliefs," is supposed to get people out of having to PROVE that their position is true...ESPECIALLY when they use those beliefs to change other peoples' lives.

Someone explain that to me. Please.

Because I'm inclined to treat such a position as utter bullshit. I'm inclined to say that, in this particular case, tolerance is quite a BAD thing...kinna like "tolerating" people shooting you in the head.